Varistor Body Surface Zr Pr Gradient for Plating Adhesion
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Solution Overview
Problem
Conventional varistors experience significant plating extension and adhesion issues during electroplating, leading to short-circuits, which are not fully addressed by existing methods such as diffusing Li or Na into the varistor body, especially when achieving deep surface resistance is difficult.
Innovation Solution
A varistor body with a composition containing ZnO as the main component and Co, Pr, and Zr as auxiliary components, where the Zr and Pr content ratios in the surface region satisfy specific conditions, reducing non-uniformity and local resistance differences, thereby minimizing plating extension and adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electroplating is applied to the varistor body, then the heat resistance of external electrodes is improved, but plating extension and plating adhesion occur causing short-circuits
Solution Approach 1:
The patent applies local quality by creating a high-resistance region specifically in the vicinity of the surface of the varistor body through Li or Na diffusion. This localized modification ensures that plating only forms on the substrate electrode and not on adjacent areas, thereby preventing plating extension and adhesion while maintaining the desired electroplating properties on the electrode surface.
Solution Approach 2:
The patent implements preliminary action by performing Li or Na diffusion into the varistor body before the electroplating process. This pre-treatment creates a high-resistance barrier in the surface region that prevents unwanted plating formation during subsequent electroplating, thereby preventing plating extension and adhesion issues before they occur.
2Object-affected harmful factors
If Li or Na is diffused into deep region of varistor body to suppress plating extension, then plating adhesion is reduced, but it becomes difficult to achieve sufficient diffusion depth
Solution Approach 1:
The patent applies parameter changes by optimizing the diffusion conditions (temperature, time, concentration) of Li or Na into the varistor body. By carefully controlling these parameters, the invention achieves sufficient diffusion depth to create an effective high-resistance barrier without making the diffusion process excessively difficult, thereby balancing plating suppression with manufacturing feasibility.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The varistor body effectively suppresses plating extension and adhesion, reducing the occurrence of short-circuits and ensuring reliable electroplating processes.
Implementation Method 1
a method of diffusing Li or Na into a region in the vicinity of surface of the varistor body
Implementation Method 2
the formation of that type of plating layer is generally done by electroplating
Data Source
AI summary
A preferred varistor body 2 has a structure of alternately laminated internal electrode layer 12 and varistor layer 14. The varistor layer 14 has a composition containing ZnO as the main component, and Co, Pr, and Zr as the auxiliary components. An analysis of the varistor body 2 in the depth direction from the surface thereof satisfies the formula (1) and (2):0.4×Z1/Z0+0.5≦P1/P0≦0.4×Z1/Z0+0.9 (1)1<Z1/Z0<2.2 (2)where, Z0 is the Zr content at a reference depth where the Zr content becomes almost constant, Z1 is the Zr content at a level of 2 μm at the surface side above the reference depth, P0 is the Pr content at the reference depth, and P1 is the Pr content at a level of 2μm at the surface side above the reference depth.